1. Technical Field of the Invention
The present invention relates to an electronic keyboard instrument and a program suitable for use with an electronic piano.
2. Description of the Related Art
On an acoustic piano, a player can generate a variety of musical sounds that differ according to a variety of articulations. These articulations can be discriminated based on the differences of velocity patterns of a key moving from its initial position toward its full stroke position. Patent References 1 and 2 describe a technology in which a key stroke from the initial position to the full stroke position is divided into a plurality of sections and respective key depression velocities in the plurality of sections are measured to allow an electronic keyboard instrument to discriminate such articulations. In this technology, a sound tone such as a soft or sharp tone is selected according to the plurality of key velocities or alternatively a sound tone is altered by amplifying its nonlinear component.
[Patent Reference 1] Japanese Patent Application Publication No. 61 (1986)-54234, and corresponding U.S. Pat. No. 4,416,178
[Patent Reference 2] Japanese Patent No. 3355743, and corresponding U.S. Pat. No. 5,619,005
However, it is not feasible, in terms of price, to equip popular electronic keyboard instruments with expensive sensors capable of measuring accurate key tracks. Accordingly, popular electronic keyboard instruments generally use sensors that detect about three depression positions on the key track to determine velocities V1 and V2 of two sections between the three depression positions. The conventional electronic keyboard instrument generates a key-on signal and starts synthesizing a musical sound signal at the time when the detection of the first and second velocities V1 and V2 is completed (i.e., when the key position reaches the third contact position). On the other hand, if the key is released when the velocity V1 has been detected and the velocity V2 has not been detected, it is determined that the ongoing key depression operation has been terminated and thus no musical sound signal is generated for the key depression operation.
However, a sophisticated articulation is occasionally performed on an acoustic piano by pressing a key at a very high velocity and releasing it before completing the key-stroke operation. In the acoustic piano, a hammer can reach a string by its inertia if sufficient kinetic energy is transferred from a key to the hammer. Therefore, such a sophisticated articulation in the acoustic piano certainly generates a musical sound. However, the conventional electronic keyboard instrument has a problem in that such a sophisticated articulation generates no musical sound signal since the key position does not reach the third contact position.
Some electronic keyboard instruments include hammer mechanisms, which simulate those of acoustic pianos, and sensors for measuring velocities of hammers included in the hammer mechanisms. These electronic keyboard instruments do not have the above problem since they obtain the hammer velocity through actual measurement in response to a key depression operation performed to generate a musical sound. However, the hammer mechanism complicates the structure of the electronic keyboard instrument and increases the cost thereof. Thus, most popular electronic keyboard instruments do not adopt hammer mechanisms.